The main properties, correlations and evolution features of disk
galaxies formed within CDM halos, under the assumption mentioned
at the beginning of this section, arise from the combination of three
cosmological factors and their statistical distributions:
the virial mass, the MAH, and the spin parameter
. The former
determines the scale. The latter ones determine
the SF history and the intensive properties, and are at the basis of
the disk HS correlations, suggesting a biparametrical nature for this
sequence
(Avila-Reese & Firmani
2000).
Observations tend to confirm this biparametrical nature (e.g,
de Blok & McGaugh
1997).
The MAH drives the gas infall rate, which determines mainly the galaxy
color indexes. The
parameter determines mainly the
disk SB, and strongly influences the rotation curve shape and the
bulge-to-disk ratio (secular bulge).
The mass galaxy fraction, fgal, which influences some disk
properties, is an astrophysical parameter determined mainly by the halo
gas dissipation and feedback efficiencies; it may vary from galaxy to
galaxy, but its value on average is around 0.03 (see
Section 3).
The shapes of the rotation curves and the SB distribution are better
reproduced jointly just for this value
(Avila-Reese et
al. 2002).

An important ingredient, which begins now to be included in
the CDM models of disk evolution, is the dynamics related to
bars, spiral arms and minor mergers (e.g., see the contributions
by Valenzuela, Athanassoula, Curir, Bertschik and others in this
volume). This ingredient, highly connected to the main disk properties
and processes described above, is at the basis of the "showy"
disk morphological signatures, which characterize the tuning
fork of the disk HS, and may play some role in the morphological
transformation due to secular processes.